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Iterating hash map values, keys without iterator allocations / JAVA

Nobody likes lags. So for some (real time) applications like real time rendered 3D games it is nessessary to avoid memory allocations and garbage collection when beeing e.g. ingame as GC might block your game just when you do not need or want it.

Additionally there is no way to control garbage collection in standard JVMs.

When profiling your application with tools like Visual VM (http://visualvm.java.net) you will notice iterators very fast as one main cause for frequent garbage collection.

While you can work around creating iterators of ArrayList using simple old for loops like

As there is no way to avoid creating iterators in theses cases I just programmed an own unordered hash map which is set up to reuse a single values and key iterator.

There is one drawback as you can not do nesting with the same hash map iterator in it self which is rarely required.

Basically a hash map does some kind of partition based on a hash function (which is provided e.g. in String.hashCode(), ..., Object.hashCode())

Here it is called buckets. Each bucket can contain several key value pairs.
The bucket is identified by the hash function of the key object. The key value pair is finally identified by Object.equals() in a bucket as a bucket can contain multiple key value pairs.

The number of buckets always equals the number of elements stored in a hash map.

In best case you would have N buckets for N elements and each bucket would contain a single key value pair.
In this case the complexity for put, get, remove would be O(1). With collisions (means multiple key value pairs in one bucket) complexity will have a little O(n) shadow.